The present invention relates generally to a nut, and in particular to a nut having a locking mechanism and requiring low operating torque.
Nuts are widely used in the mechanical industry for securing parts of a machine, such as a grinding wheel of a grinding machine and a saw blade of a circular saw machine. The grinding wheel or the saw blade is usually secured by a nut engaging a threaded axle. When the axle rotates, it drives the grinding wheel or the same blade to rotate in unison therewith. To ensure operation safety, hand tools are commonly employed to securely tighten the nut for properly fixing the grinding wheel or the saw blade to the axle. Such an operation is quite time and labor consuming. In addition, the nut may inadvertently be not tightly secured by an absent-minded operator. Risk of damage to the operator or other properties arises with a xe2x80x9cflyingxe2x80x9d grinding wheel or saw blade unexpectedly leaving the axle of the machine.
It is thus desired to have a nut that overcomes the above problems.
An object of the present invention is to provide a nut having a locking mechanism for securely retaining the nut on a threaded axle or bolt without unexpectedly separating from the axle or bolt.
Another object of the present invention is to provide a nut that can be loosened with a small torque.
To achieve the above objects, in accordance with the present invention, there is provided a nut comprising a base portion forming an inner threaded bore and a first sun gear. cap forms a second sun gear of which the teeth is different from that of the first sun gear. The cap is rotatably mounted to the base with the first and second sun gears opposing and coaxial with each other. A control ring carries planetary gears engaging both the first and second sun gears. The nut secures a rotatable member of a rotary machine to a threaded driving axle. The nut is initially and loosely tightened on the axle by manually rotating the control ring. The cap has a high friction surface engaging the rotatable member. When the axle starts to rotate, a relative rotation occurs between the rotatable member and the axle which causes the cap to rotate with respect to the base. The rotation of the cap is transmitted to the base by the planetary gears to securely and completely tighten the nut. To release the nut, manual rotation of the control ring causes the base to rotate therewith in a speed reduced fashion due to the difference in teeth between the cap and the base. A small torque applied to the control ring is then converted into a large torque acting upon the base to readily loosen the nut.